Abstract
Sensitive and reliable detection of tumour markers is of great significance for early diagnosis and monitoring recurrence of cancers. Herein, a simple electrochemical immunosensor is developed with an integrated electrochemical probe on the sensing surface, which is able to sensitively and reagentlessly detect the breast cancer biomarker, human epidermal growth factor receptor 2 (ErbB2). Ferrocene (Fc) is chosen as the signal indicator and covalently grafted on cationic polyelectrolyte poly(ethylene imine) (Fc-PEI). The redox Fc-PEI could alternately assemble with carboxyl functionalized single-walled carbon nanotubes (SWNTs) on an indium tin oxide electrode through layer-by-layerelectrostatic assembly. After Anti-ErbB2 antibody is covalently immobilized onto the outermost SWNTs layer followed by blocking the electrode with bovine serum albumin, a sensing interface with recognitive probe and electrochemical probe is obtained. In the presence of ErbB2, the formed antigen–antibody complex makes a barrier to inhibit electro-transfer of inner Fc, leading to a decreased electrochemical response. Owing to the SWNTs-facilitated charge transfer and abundant surface-bound probes, the developed sensor demonstrates outstanding performance for reagentless detection of ErbB2 in terms of wide detection range (1.0–200.0 ng mL−1) and low detection limit (0.22 ng mL−1). The developed immunosensor also exhibits good selectivity, reproducibility and stability. Real analysis of ErbB2 in human serum samples is also demonstrated.
Highlights
Diagnosis of cancers is crucial for providing the appropriate treatment processes and increasing the survival rate
We demonstrate an electrochemical immunosensor with surface-con ned electrochemical probe for sensitive and reagentless detection of breast cancer biomarker ErbB2
Through layer-by-layer (LBL) electrostatic assembly between Fc-Poly(ethylene imine) (PEI) and carboxyl functionalized single-walled carbon nanotubes (SWNTs), abundant Fc signal molecules are con ned in Fc-PEI/ SWNTs multilayers supported by ITO electrode
Summary
Diagnosis of cancers is crucial for providing the appropriate treatment processes and increasing the survival rate. Sensitive and reliable detection of low-levels of tumour markers is of great signi cance in early diagnosis and monitoring recurrence of cancers.[1,2] Human epidermal growth factor receptor 2 (ErbB2), as an important tumour biomarker,[3,4,5] is over-expressed in around 20–25% of invasive breast cancers and plays a major role in promoting breast cancer cell proliferation and malignant growth.[6,7] Currently, several methods have been used for diagnostic tests of ErbB2, including enzyme-linked immuno-sorbent assay and in situ uorescent hybridization.[3,8] most of these techniques provide only semi-qualitative results separating patients into HER2 positive and HER2 negative They are usually complicated and time-consuming, need exhaustive sample pre-treatment, and require specially trained personnel to perform the complex procedures. Owing to the electronic wire action of nanotubes and abundant surface-bound probes, the developed sensor demonstrates outstanding performance for reagentless detection of ErbB2 in terms of wide detection range, low detection limit, good selectivity, reproducibility and stability
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